Sunday, 16 May 2010

New rudder finished

How to make a rudder.

First buy some expensive western red cedar, cut into strips a little over half the thickness and twice the length the rudder is going to be, and glue the strips together with epoxy and high density filler. So you end up with a block of wood as thick and wide as the rudder is going to be, and twice the length.

Then you need to choose the right profile. I measured the rudder from the other hull, and figured it was intended to be a NACA 0014 profile, but it wasn't that accurate. To make a more accurate shape I used a spreadsheet here, and made a paper template which was a half profile of the rudder. I then drew round the shape at each end of the block of wood, and planed the length to the shape:

Lots of that expensive wood ends up in shavings on the floor. The black thing on the right is the rudder I'm copying. I've shaped the block, cut it in half, and then cut round the sides. The two halves almost ready to join together. But I needed to make glue the stainless steel rudder stock in first, so I routed and chiseled the other side:

And then glued the rudder stock in with epoxy and high density filler.

The wood was beginning to warp a little - each half began to bend outward a bit. I guess that was due to the way the grain was running, but once the two halves are glued together, that tendency to warp should be balanced out.

Here's the two halves joined together and planed and sanded to the final shape. Did I mention the sanding? No? Well, there was a lot of that, and not with a machine either, but with a long board with sandpaper stapled to it. That way, you don't end up sanding hollows into the wood. Hard work, and the dust being pretty toxic, all done wearing a face mask.

Here's the rudder finished - coated in epoxy and glass cloth. At the aft edge, the layers of glass are brought together and filled with epoxy filler. This is stronger than a wooden edge, as its getting pretty thin back there.

The final coat of epoxy is dry - now it just needs a light sanding, and then painting with a couple of coats of antifoul.

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